Method and device for receiving downlink signal

ABSTRACT

The present invention relates to A METHOD AND A DEVICE FOR RECEIVING A DOWNLINK SIGNAL IN A WIRELESS COMMUNICATION SYSTEM. More specifically, the method of the present invention comprises the following steps: receiving first control information for downlink scheduling in the first slot of a resource block pair, wherein the first control information includes allocation information on at least one resource unit; receiving a data in the second slot of the resource block pair, when the allocation information on the resource unit having the resource block pair with the first control information has a first value; and attempting to detect second control information for uplink scheduling in the second slot of the resource block pair, when the allocation information on the resource unit having the resource block pair with the first control information has a second value.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT/KR2011/002633 filed onApr. 13, 2011, which claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application Nos. 61/323,842 filed on Apr. 13, 2010,61/324,304 filed on Apr. 15, 2010, 61/327,086 filed on Apr. 22, 2010,61/334,159 filed on May 12, 2012, 61/334,101 filed on May 12, 2010,61/334,186 filed on May 13, 2010, 61/346,008 filed on May 18, 2010,61/349,211 filed on May 28, 2010, 61/351,302 filed on Jun. 4, 2010, andunder 35 U.S.C. §119(a) to Patent Application No. 10-2011-0034204 filedin the Republic of Korea on Apr. 13, 2011, all of which are herebyexpressly incorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a radio communication system, and moreparticularly, to a method and device for receiving a downlink signal.

BACKGROUND ART

Radio communication systems have been diversified in order to providevarious types of communication services such as voice or data service.In general, a radio communication system is a multiple access systemcapable of sharing available system resources (bandwidth, transmit poweror the like) so as to support communication with multiple users.Examples of the multiple access system include a Code Division MultipleAccess (CDMA) system, a Frequency Division Multiple Access (FDMA)system, a Time Division Multiple Access (TDMA) system, an OrthogonalFrequency Division Multiple Access (OFDMA) system, a Single CarrierFrequency Division Multiple Access (SC-FDMA) system, and the like.

DISCLOSURE Technical Problem

An object of the present invention is to provide a method and device forefficiently utilizing downlink resources in a radio communicationsystem.

The technical problems solved by the present invention are not limitedto the above technical problems and other technical problems which arenot described herein will become apparent to those skilled in the artfrom the following description.

Technical Solution

According to an aspect of the present invention, A method for receivingdownlink signal in a wireless communication system, the methodcomprising: receiving first control information for downlink schedulingin the first slot of a resource block (RB) pair, wherein the firstcontrol information includes allocation information on one or moreresource units; receiving data at the second slot of the RB pair whenthe allocation information on a resource unit including the resourceblock pair with the first control information has a first value; andattempting to detect second control information for uplink scheduling atthe second slot of the RB pair when the allocation information on theresource unit including the resource block pair with the first controlinformation has a second value.

According to other aspect of the present invention, An user equipmentconfigured to receive a downlink signal in a wireless communicationsystem, the apparatus comprising: a radio frequency unit; and aprocessor, wherein the processor is configured to receive first controlinformation for downlink scheduling in the first slot of a resourceblock (RB) pair, wherein the first control information includesallocation information on one or more resource units, and to receivedata at the second slot of the RB pair when the allocation informationon a resource unit including the resource block pair with the firstcontrol information has a first value, and to attempt to detect secondcontrol information for uplink scheduling at the second slot of the RBpair when the allocation information on the resource unit including theresource block pair with the first control information has a secondvalue.

Preferably, the resource unit allocation information includes bitmap forresource allocation, each bit indicating resource allocation of acorresponding RB or a RBG (Resource Block Group).

Preferably, the second control information exists on the second slot ofthe RB pair when the allocation information on the resource unitincluding the resource block pair with the first control information hasthe second value.

Preferably, the first value is 1, and the second value is 0.

Preferably, the attempting to detect the second control information isperformed under an assumption that an aggregation level of the secondcontrol information is less than a control level of the first controlinformation.

Preferably, the attempting to detect the second control information isperformed only on resource overlapped between pre-configured searchspace for the second control information and the resource unit for whichthe allocation information has the second value.

Preferably, further comprising: receiving information related toarrangement of the second control information on resources of the secondslot via an upper layer signaling.

Advantageous Effects

According to a communication system of the present invention, it ispossible to efficiently utilize downlink resources in a radiocommunication system.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing the structure of a radio frame used in a3^(rd) Generation Partnership Project (3GPP) system.

FIG. 2 is a diagram showing a resource grid of a downlink slot.

FIG. 3 is a diagram showing the structure of a downlink subframe.

FIG. 4 is a diagram showing the structure of an uplink subframe used ina system.

FIG. 5 is a diagram showing a process of transmitting a signal using amulti-antenna scheme.

FIG. 6 is a diagram showing the structure of a demodulation referencesignal (DM RS).

FIG. 7 is a diagram showing a method of mapping a virtual resource block(VRB) to a physical resource block (PRB).

FIGS. 8 to 10 are diagrams showing Type 0 resource allocation (RA), Type1 RA and Type 2 RA, respectively.

FIG. 11 is a diagram showing a radio communication system including arelay.

FIG. 12 is a diagram showing backhaul communication using a multimediabroadcast over a single frequency network (MBSFN) subframe.

FIGS. 13 to 14 are diagrams showing arbitrary division of frequency-timeresources.

FIGS. 15 to 17 are diagrams showing examples of placing and demodulatingan R-PDCCH/(R-)PDSCH.

FIGS. 18 to 19 are diagrams showing examples of dividing an RB pair intoa plurality of RE groups.

FIG. 20 to 23 are diagrams showing other examples of placing anddemodulating R-PDCCHs/(R-)PDSCHs.

FIG. 24 is a diagram showing the case of transmitting UL grant only inthe case in which a DL RA bit is set to 0.

FIGS. 25 to 27 are diagrams showing a method of indicating a resourceuse state of a second slot.

FIG. 28 is a diagram showing a downlink control information (DCI)format.

FIGS. 29 to 42 are diagrams showing various methods of indicating aresource use state of a second slot.

FIGS. 43 to 46 are diagrams showing a method of ordering indexes ofrelay physical downlink control channels (R-PDCCHs) and a resourceallocation example thereof.

FIG. 47 is a diagram showing a base station, a relay node and a userequipment (UE).

BEST MODE

The configuration, the operation and the other features of theembodiments of the present invention will be described with reference tothe accompanying drawings. The following embodiments of the presentinvention may be utilized in various radio access systems such as a CodeDivision Multiple Access (CDMA) system, a Frequency Division MultipleAccess (FDMA) system, a Time Division Multiple Access (TDMA) system, anOrthogonal Frequency Division Multiple Access (OFDMA) system, or aSingle Carrier Frequency Division Multiple Access (SC-FDMA) system. TheCDMA system may be implemented as radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. The TDMA system may beimplemented as radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). The OFDMA system may be implemented asradio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802-20 or E-UTRA (Evolved UTRA). The UTRA system is part of theUniversal Mobile Telecommunications System (UMTS). A 3^(rd) GenerationPartnership Project Long Term Evolution (3GPP LTE) communication systemis part of the E-UMTS (Evolved UMTS) which employs the E-UTRA. TheLTE-Advanced (LTE-A) is an evolved version of the 3GPP LTE.

The following embodiments focus on the 3GPP system to which thetechnical features of the present invention are applied, but the presentinvention is not limited thereto.

FIG. 1 is a diagram showing the structure of a radio frame of a 3^(rd)Generation Partnership Project (3GPP) system.

Referring to FIG. 1, the radio frame has a length of 10 ms(307200·T_(s)) and includes 10 subframes with the same size. Each of thesubframes has a length of 1 ms and includes two slots. Each of the slotshas a length of 0.5 ms (15360·T_(s)). T_(s) denotes a sampling time, andis represented by T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸ (about 33 ns). Eachslot includes a plurality of OFDM symbols or SC-FDMA symbols in a timedomain, and includes a plurality of resource blocks (RBs) in a frequencydomain. In the LTE system, one RB includes 12 subcarriers×7(6) OFDMsymbols. A Transmission Time Interval (TTI) which is a unit time fortransmission of data may be determined in units of one or moresubframes. The structure of the radio frame is only exemplary and thenumber of subframes, the number of subslots, or the number ofOFDM/SC-FDMA symbols may be variously changed in the radio frame.

FIG. 2 is a diagram showing a resource grid of a downlink slot.

Referring to FIG. 2, a downlink slot includes a plurality of OFDMsymbols (e.g., seven) in a time domain and N^(DL) _(RB) RBs in afrequency domain. Since each RB includes 12 subcarriers, the downlinkslot includes N^(DL) _(RB)×12 subcarriers in the frequency domain.Although FIG. 2 shows the case in which the downlink slot includes sevenOFDM symbols and the RB includes 12 subcarriers, the present inventionis not limited thereto. For example, the number of OFDM symbols includedin the downlink slot may be changed according to the length of a cyclicprefix (CP). Each element of the resource grid is referred to as aresource element (RE). The RE is a minimum time/frequency resourcesdefined in a physical channel and is indicated by one OFDM symbol indexand one subcarrier index. One RB includes N^(DL) _(symb)×N^(RB) _(sc)REs. N^(DL) _(symb) denotes the number of OFDM symbols in the downlinkslot and N^(RB) _(sc) denotes the number of subcarriers included in theRB. The number N^(DL) _(RB) of RBs included in the downlink slot dependson a downlink transmission bandwidth set in a cell.

The downlink slot structure shown in FIG. 2 is equally applied to anuplink slot structure. At this time, the uplink slot structure includesSC-FDMA symbols, instead of the OFDM symbols.

FIG. 3 is a diagram showing the structure of a downlink subframe in a3GPP system.

Referring to FIG. 3, one or more OFDM symbols located in a front portionof the subframe are used as a control region and the remaining OFDMsymbols are used as a data region. The size of the control region may beindependently set per subframe. The control region is used to transmitscheduling information and layer 1/layer 2 (L1/L2) control information.The data region is used to transmit traffic. The control channelincludes a Physical Control Format Indicator Channel (PCFICH), aPhysical Hybrid automatic repeat request (ARQ) Indicator Channel(PHICH), a Physical Downlink Control Channel (PDCCH), etc. The trafficchannel includes a Physical Downlink Shared Channel (PDSCH).

The PDCCH may inform a UE or a UE group of resource allocationinformation about resource allocation of a paging channel (PCH) or aDownlink Shared Channel (DL-SCH) which is a transport channel, uplinkscheduling grant, HARQ information, etc. The PCH and the DL-SCH aretransmitted through a PDSCH. Accordingly, an eNode B and a UE generallytransmit and receive data through a PDSCH except for specific controlinformation or specific service data. Control information transmittedthrough a PDCCH is referred to downlink control information (DCI). TheDCI indicates uplink resource allocation information, downlink resourceallocation information and an uplink transmit power control command forarbitrary UE groups. The eNode B decides a PDCCH format according to DCIto be sent to the UE and attaches a cyclic redundancy check (CRC) tocontrol information. The CRC is masked with a unique identifier (e.g., aRadio Network Temporary Identifier (RNTI)) according to an owner orusage of the PDCCH.

FIG. 4 is a diagram showing the structure of an uplink subframe used ina 3GPP system.

Referring to FIG. 4, a subframe 500 having a length of 1 ms which is abasic unit of LTE uplink transmission includes two slots 501 each havinga length of 0.5 ms. In the case of a length of a normal Cyclic Prefix(CP), each slot includes seven symbols 502 and one symbol corresponds toone Single carrier-Frequency Division Multiple Access (SC-FDMA) symbol.An RB 503 is a resource allocation unit corresponding to 12 subcarriersin a frequency domain and one slot in a time domain. The structure ofthe uplink subframe of the LTE system is roughly divided into a dataregion 504 and a control region 505. The data region refers tocommunication resources used for data transmission, such as voice orpackets transmitted to each UE, and includes a physical uplink sharedchannel (PUSCH). The control region refers to communication resourcesused to transmit an uplink control signal such as a downlink channelquality report from each UE, reception ACK/NACK of a downlink signal, anuplink scheduling request or the like, and includes a Physical UplinkControl Channel (PUCCH). A sounding reference signal (SRS) istransmitted through a last SC-FDMA symbol of one subframe on a timeaxis. SRSs of several UEs transmitted through the last SC-FDMA of thesame subframe are distinguished according to a frequencyposition/sequence.

FIG. 5 is a diagram showing a process of transmitting a signal using amulti-antenna scheme.

Referring to FIG. 5, codewords are scrambled by scrambling modules 301.The codeword includes an encoded bit stream corresponding to a transportblock. The scrambled codewords are input to modulation mappers 302 andare modulated into complex symbols using a Binary Phase Shift Keying(BPSK), Quadrature Phase Shift Keying (QPSK) or 16-Quadrature amplitudemodulation (QAM) scheme according to the kind of the transmitted signaland/or the channel state. Thereafter, the modulated complex symbols aremapped to one or more layers by a layer mapper 303. Codeword-to-layermapping may be changed according to a transmission scheme. Thelayer-mapped signals may be multiplied by a predetermined precodingmatrix selected according to a channel state by a precoding module 304to be allocated to transmission antennas. The signals to be transmittedby the antennas may be mapped to time-frequency resource elements to beused for transmission by the resource element mappers 305, andtransmitted via OFDMA signal generator 306 and antennas.

FIG. 6 is a diagram showing the structure of a demodulation referencesignal (DM RS). The DM RS is a UE-specific RS used to demodulate asignal of each layer when a signal is transmitted using multipleantennas. The DM RS is used to demodulate a PDSCH and an R-PDSCH. Sincean LTE-A system includes a maximum of eight transmission antennas, amaximum of eight layers and DM RSs therefor are necessary. Forconvenience, DM RSs for layers 0 to 7 are referred to as DM RSs (layers)0 to 7.

Referring to FIG. 6, the DM RSs for two or more layers share the same REand are multiplexed according to a code division multiplexing (CDM)scheme. More specifically, DM RSs for layers are spread using spreadingcodes (e.g., Walsh codes or orthogonal codes such as DFT codes) and aremultiplexed on the same RE. For example, DM RSs for layers 0 and 1 sharethe same RE and are, for example, spread on two REs of OFDM symbols 12and 13 at a subcarrier 1 (k=1) using orthogonal coding. That is, in eachslot, the DM RSs for layers 0 and 1 are spread along a time axis usingcodes having a spreading factor (SF) of 2 and are multiplexed on thesame REs. For example, the DM RS for the layer 0 may be spread using [+1+1] and the MD RS for the layer 1 may be spread using [+1 −1].Similarly, the DM RSs for layers 2 and 3 are spread on the RE usingdifferent orthogonal codes. The DM RSs for layers 4, 5, 6 and 7 arespread on the REs occupied by the DM RSs for layers 0, 1, 2 and 3 usingcodes orthogonal to the layers 0, 1, 2 and 3. Codes having SF=2 is usedfor the DM RS if four or less layers are used and codes having SF=4 isused for the DM RS if five or more layers are used. In LTE-A, antennaports for the DM RS is {7, 8, . . . , n+6} (n being the number oflayers).

Table 1 shows a spread sequence for antenna ports 7 to 14 defined inLTE-A.

TABLE 1 Antenna port p [ w _(p) (0) w _(p) (1) w _(p) (2) w _(p) (3)] 7[+1 +1 +1 +1] 8 [+1 −1 +1 −1] 9 [+1 +1 +1 +1] 10 [+1 −1 +1 −1] 11 [+1 +1−1 −1] 12 [−1 −1 +1 +1] 13 [+1 −1 −1 +1] 14 [−1 +1 +1 +1]

Referring to Table 1, orthogonal code for antenna ports 7 to 10 has astructure in which orthogonal code having a length of 2 is repeated. Asa result, orthogonal code having a length of 2 is used at a slot levelif four or less layers are used and orthogonal code having a length of 4is used at a subframe level if 5 or more layers are used.

Hereinafter, resource block mapping will be described. A physicalresource block (PRB) and a virtual resource block (VRB) are defined. ThePRB is equal to that shown in FIG. 2. That is, the PRB is defined asN_(symb) ^(DL) contiguous OFDM symbols in a time domain and N_(sc) ^(RB)contiguous subcarriers in a frequency domain. PRBs are numbered from 0to N_(RB) ^(DL)−1 in the frequency domain. A relationship between a PRBnumber n_(PRB) and an RE (k, l) in a slot is shown in Equation 1.

$\begin{matrix}{n_{PRB} = \lfloor \frac{k}{N_{sc}^{RB}} \rfloor} & {{Equation}\mspace{14mu} 1}\end{matrix}$

where, k denotes a subcarrier index and N_(sc) ^(RB) denotes the numberof subcarriers included in one RB.

The VRB has the same size as the PRB. A localized VRB (LVRB) of alocalized type and a distributed VRB (DVRB) of a distributed type aredefined. Regardless of the type of the VRB, a pair of RBs is allocatedover two slots by a single VRB number n_(VRB).

FIG. 7 is a diagram showing a method of mapping a virtual resource block(VRB) to a physical resource block (PRB).

Referring to FIG. 7, since an LVRB is directly mapped to a PRB, a VRBnumber n_(VRB) equally corresponds to a PRN number n_(PRB)(n_(PRB)=n_(VRB)). The VRB is numbered from 0 to N_(VRB) ^(DL)−1 andN_(VRB) ^(DL)=N_(RB) ^(DL). The DVRB is mapped to the PRB after beinginterleaved. More specifically, the DVRB may be mapped to the PRB asshown in Table 2. Table 2 shows an RB gap value.

TABLE 2 Gap (N _(gap)) System BW (N _(RB) ^(DL)) 1^(st) Gap (N _(gap,1))2^(nd) Gap (N _(gap,2))  6-10 [N _(RB) ^(DL)/2] N/A 11 4 N/A 12-19 8 N/A20-26 12 N/A 27-44 18 N/A 45-49 27 N/A 50-63 27  9 64-79 32 16  80-11048 16

N_(gap) denotes a frequency gap (e.g., PRB unit) when VRBs having thesame number are mapped to PRBs of a first slot and a second slot. Incase of 6≦N_(RB) ^(DL)≦49 only one gap value is defined(N_(gap)=N_(gap,1)). In case of 50≦N_(RB) ^(DL)≦110, two gap valuesN_(gap,1) and N_(gap,2) are defined. N_(gap)=N_(gap,1) orN_(gap)=N_(gap,2) is signaled through downlink scheduling. DVRBs arenumbered from 0 to N_(VRB) ^(DL)−1, is N_(VRB) ^(DL)=N_(VRB,gap1)^(DL)=2·min(N_(gap),N_(RB) ^(DL)−N_(gap)) with respect toN_(gap)=N_(gap,1), and is N_(VRB) ^(DL)=N_(VRB,gap2) ^(DL)=└N_(RB)^(DL)/2N_(gap)┘·2N_(gap) with respect to N_(gap)=N_(gap,2). min(A,B)denotes the smaller of A or B.

Contiguous Ñ_(VRB) ^(DL) v VRB numbers configure a unit for VRB numberinterleaving, is Ñ_(VRB) ^(DL)=N_(VRB) ^(DL) in case ofN_(gap)=N^(gap,1), and is Ñ_(VRB) ^(DL)=2N_(gap) in case ofN_(gap)=N_(gap,2). VRB number interleaving of each interleaving unit maybe performed using four columns and N_(row) rows. N_(row)=┌Ñ_(VRB)^(DL)/(4P)┐·P and P denotes the size of a Resource Block Group (RBG).The RBG is defined by P contiguous RBs. The VRB number is written in amatrix on a row-by-row basis and is read in a column-by-column basis.N_(null) null values are inserted into last N_(null)/2 rows of secondand fourth columns and N_(null)=4N_(row)−Ñ_(VRB) ^(DL). The null valueis ignored upon reading.

Hereinafter, resource allocation defined in LTE will be described. FIGS.8 to 10 are diagrams showing control information formats for Type 0resource allocation (RA), Type 1 RA and Type 2 RA and resourceallocation examples thereof, respectively.

A user equipment (UE) interprets a resource allocation field based on adetected PDCCH DCI format. The resource allocation field in each PDCCHincludes two parts: a resource allocation header field and actualresource block allocation information. PDCCH DCI formats 1, 2 and 2A forType 0 and Type 1 RA have the same format and are distinguished via asingle bit resource allocation header field present according to adownlink system bandwidth. More specifically, Type 0 RA is indicated by0 and Type 1 RA is indicated by 1. While PDCCH DCI formats 1, 2 and 2Aare used for Type 0 or Type 1 RA, PDCCH DCI formats 1A, 1b, 1C and 1Dare used for Type 2 RA. The PDCCH DCI format having Type 2 RA does nothave a resource allocation header field.

Referring to FIG. 8, in Type 0 RA, resource block allocation informationincludes a bitmap indicating an RBG allocated to a UE. The RBG is a setof contiguous PRBs. The size P of the RBG depends on a system bandwidthas shown in Table 3.

TABLE 3 System Bandwidth RBG Size N _(RB) ^(DL) (P) <10 1 11-26 2 27-633  64-110 4

In a downlink system bandwidth having N_(RB) ^(DL), the total numberN_(RBG) of RBGs is N_(RBG)=┌N_(RB) ^(DL)/P┐, the size of └N_(RB)^(DL)/P┘ RBGs is P, and the size of one RBG is N_(RB) ^(DL)−P·└N_(RB)^(DL)/P┘ in case of N_(RB) ^(DL) mod P>0. Mod denotes a modulooperation, ┌ ┐ denotes a ceiling function, and └ ┘ denotes a flooringfunction. The size of a bitmap is N_(RBG) and each bit corresponds toone RBG. All RBGs are indexed by 0 to N_(RBG)−1 in a frequency increasedirection and RBG 0 to RBG N_(RBG)−1 are mapped from a most significantbit (MSB) to a least significant bit (LSB) of a bitmap.

Referring to FIG. 9, in Type 1 RA, resource block allocation informationhaving the size of N_(RBG) informs a scheduled UE of resources in an RBGsubset in PRB units. The RBG subset p (0≦p<P) starts from an RBG p andincludes every P-th RBG. The resource block allocation informationincludes three fields. A first field has ┌log₂(P)┐ bits and indicates anRBG subset selected from among P RBG subsets. A second field has 1 bitand indicates resource allocation span shift within a subset. Shift istriggered if a bit value is 1 and is not triggered if a bit value is 0.A third field includes a bitmap and each bit indicates one PRB within aselected RBG set. The size of a bitmap part used to indicate a PRBwithin the selected RBG subset is N_(RB) ^(TYPE1) and is defined byEquation 2.N _(RB) ^(TYPE1) =┌N _(RB) ^(DL) /P┐−┌log₂(P)┐−1  Equation 2

An addressable PRB number in the selected RBG subset may start from anoffset Δ_(shift)(p) from a smallest PRB number within the selected RBGsubset and may be mapped to a MSB of a bitmap. The offset is representedby the number of PRBs and is applied within the selected RBG subset. Ifthe bit value within a second field for resource allocation span shiftis set to 0, an offset for an RBG subset p is Δ_(shift)(p)=0. In theother case, an offset for an RBG subset p is Δ_(shift)(p)=N_(RB)^(RBG subset)(p)−N_(RB) ^(TYPE1). N_(RB) ^(RBG subset)(p) denotes thenumber of PRBs within the RBG subset p and may be obtained by Equation3.

$\begin{matrix}{{N_{RB}^{{RBG}\mspace{11mu}{subset}}(p)} = \{ \begin{matrix}{{{\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \rfloor \cdot P} + P},} & {p < {\lfloor \frac{N_{RB}^{DL} - 1}{P} \rfloor{mod}\mspace{14mu} P}} \\{{{\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \rfloor \cdot P} + {( {N_{RB}^{DL} - 1} ){mod}\; P} + 1},} & {p = {\lfloor \frac{N_{RB}^{DL} - 1}{P} \rfloor{mod}\mspace{14mu} P}} \\{{\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \rfloor \cdot P},} & {p > {\lfloor \frac{N_{RB}^{DL} - 1}{P} \rfloor{mod}\mspace{14mu} P}}\end{matrix} } & {{Equation}\mspace{14mu} 3}\end{matrix}$

Referring to FIG. 10, in Type 2 RA, resource block allocationinformation indicates an LVRB or DVRB set contiguously allocated to ascheduled UE. If resource allocation is signaled in PDCCH DCI format 1A,1B or 1C, a 1-bit flag indicates whether an LVRB or DVRB is allocated(e.g., 0 denotes LVRB allocation and 1 denotes DVRB allocation). Incontrast, if resource allocation is signaled in PDCCH DCI format 1C,only DVRB is always allocated. A Type 2 RA field includes a resourceindication value (RIV) and the RIV corresponds to a start resource blockRB_(start) and a length. The length denotes the number of virtually andcontiguously allocated resource blocks.

FIG. 11 is a diagram showing a communication system including a relay(or a relay node (RN)). The relay is installed in a shadow area so as toextend a service area of a base station and to improve a service.Referring to FIG. 11, a radio communication system includes a basestation (BS), a relay and a UE. The UE performs communication with thebase station or the relay. For convenience, a UE which performscommunication with the base station is referred to as a macro UE and aUE which performs communication with the relay is referred to as a relayUE. A communication link between the base station and the macro UE isreferred to as a macro access link and a communication link between therelay and the relay UE is referred to as a relay access link. Inaddition, a communication link between the base station and the relay isreferred to as a backhaul link.

The relay may be divided into an L1 (layer 1) relay, an L2 (layer 2)relay and an L3 (layer 3) relay depending on how many functions areperformed in multi-hop transmission. These relays will be brieflydescribed. The L1 relay functions as a general repeater, amplifies asignal from a BS/UE and transmits the amplified signal to a UE/BS. Sincethe relay does not perform decoding, transmission delay is short, but asignal and noise cannot be distinguished and thus noise may be alsoamplified. In order to overcome this problem, an advanced repeater or asmart repeater having a UL power control function or a self-interferencecancellation function may be used. The operation of the L2 relay may berepresented by decode-and-forward and user plane traffic may betransmitted by the L2 relay. Noise is not amplified, but delay isincreased due to decoding. The L3 relay is also referred to asself-backhauling and IP packets may be transmitted by the L3 relay. TheL3 relay has a radio resource control functions as a small base station.

The L1 and L2 relay is a part of a donor cell covered by a BS. If therelay is a part of the donor cell, since the relay cannot control a cellthereof and UEs of the cell, the relay cannot have a cell ID thereof.However, the relay may have a relay ID. In this case, some functions ofradio resource management (RRM) are controlled by the BS of the donorcell and a part of RRM may be located at the relay. The L3 relay cancontrol a cell thereof. In this case, the relay may manage one or morecells and each cell managed by the relay may have a uniquephysical-layer cell ID. The relay may have the same RRM mechanism as theBS. From the viewpoint of the UE, it makes no difference whether the UEaccesses the cell managed by the relay or the cell managed by the BS.

In addition, the relay is divided as follows according to mobility.

-   -   Fixed RN: This relay is permanently fixed and is used to        increase cell coverage or to eliminate a shadow area and may        function as a repeater.    -   Nomadic RN: This relay is temporarily installed when the number        of users is abruptly increased and may be arbitrarily moved        within a building.    -   Mobile RN: This relay may be installed in public transportation        such as a bus or a subway and may be moved.

In addition, a link between a relay and a network is divided as follows.

-   -   In-band connection: A network-to-relay link and a network-to-UE        link share the same frequency band within a donor cell.    -   Out-band connection: A network-to-relay link and a network-to-UE        link use different frequency bands within a donor cell.

The relay is divided depending on whether a UE recognizes presence ofthe relay.

-   -   Transparent relay: The UE is not aware of whether communication        with the network is performed via a relay.    -   Non-transparent relay: The UE is aware of whether communication        with the network is performed via a relay.

FIG. 12 is a diagram showing backhaul communication using a multimediabroadcast over a single frequency network (MBSFN) subframe. In anin-band relay mode, a BS-relay link (that is, a backhaul link) and arelay-UE link (that is, a relay access link) operate in the samefrequency band. If a relay transmits a signal to a UE while receiving asignal from a BS and vice versa, since a transmitter and a receiver ofthe relay cause interference, simultaneous transmission/reception of therelay may be prevented. In order to prevent simultaneoustransmission/reception, a backhaul link and a relay access link arepartitioned using a TDM scheme. In LTE-A, a backhaul link is set in anMBSFN subframe in order to support a measurement operation of a legacyLTE UE present in a relay zone (a fake MBSFN method). If an arbitrarysubframe is signaled as an MBSFN subframe, since a UE receives only acontrol (ctrl) region of the subframe, a relay may configure a backhaullink using a data region of the subframe. For example, a relay PDCCH(R-PDCCH) is transmitted using a specific resource region from a thirdOFDM symbol to a last OFDM symbol of an MBSFN subframe.

Embodiment

FIGS. 13 to 14 are diagrams showing arbitrary division of frequency-timeresources. FIG. 13 shows the case of using a single antenna port andFIG. 14 shows the case of using multiple antenna ports. These figuresshow part of a downlink subframe.

In FIG. 13, the size of a frequency-time domain denoted by X-Y may bevariously configured. In an LTE system, a resource region X-1 (X=1, 2,3) may include 12 subcarriers in a frequency domain and four OFDMsymbols in a time domain. A resource region X-2 (X=1, 2, 3) may include12 subcarriers in a frequency domain and seven OFDM symbols in a timedomain. The number of symbols may be changed according to the length ofa cyclic prefix. The number of symbols and the number of subcarriers mayhave different values according to system. In other words, the resourceregion X-1 may be part of a first slot and the resource region X-2 maybe part of a second slot. Such a resource configuration may typicallyappear in a backhaul subframe between a BS and a relay. In this case,FIG. 13 shows the remaining part of the MBSFN subframe of FIG. 12 exceptfor the control information region.

FIG. 13 shows a resource block (RB) and a resource block group (RBG) inorder to represent a resource size in a frequency domain. The RB isdefined in slot units as shown in FIG. 2. Accordingly, X-Y correspondsto one RB and [X-1, X-2] corresponds to an RB pair. Unless specificallystated, the RB may be [X-1], [X-2] or [X-1, X-2] according to context.The RBG includes one or more contiguous RBs. Although the number of RBsconfiguring the RBG is 3 in FIG. 13, the number of RBs configuring theRBG may be changed according to a system bandwidth as shown in Table 3.The RB means a PRB or a VRB.

In FIG. 14, the size of the frequency domain and the size of the timedomain in a resource region denoted by Px-yy (x, y=0, 1, 2, 3) may bevariously configured. The basic resource configuration is equal to thatdescribed with reference to FIG. 13. In the figure, Pn (n=0, 1, 2, 3, .. . ) denotes a port or layer used in a multi-layer transmission system(e.g., an MIMO system). The port or layer means a distinguishableresource region capable of transmitting different information. Themeaning of the port or layer may be differently interpreted according tosystem. For example, in a 3GPP LTE system, if P0-12 is one RB, P0-12 mayinclude 12 subcarriers in the frequency domain and seven OFDM symbols inthe time domain. If P0-12 is one RBG (e.g., RBG=4), the size of P0-12 inthe frequency domain quadruples. A Px-y1 region includes REs, the numberof which is equal to or less than the number of REs of a Px-y2 region.For example, if the Px-y1 resource region is one RB, the Px-y1 resourceregion may include 12 subcarriers and four OFDM symbols. If the Px-y1resource region is one RBG, the size of the Px-y1 resource region in thefrequency domain is increased by a multiple of the RBG unit. The Px-y1region may mean a first slot or a part thereof and the Px-y2 region maymean a second slot or a part thereof. The number of symbols may bechanged according to cyclic prefix length. The number of symbols and thenumber of subcarriers may have different values according to system.

Hereinafter, how control information and data are allocated andtransmitted in the resource configuration shown in FIGS. 13 to 14 willbe described. Unless specifically stated, a single antenna port will befocused upon and a resource region is represented by the method of FIG.13, for convenience of description. It is apparent to those skilled inthe art that the description of the single antenna port is applicable tomultiple antenna ports.

Control information (e.g., R-PDCCH) used in a link between a BS and arelay is preferably transmitted in a predetermined specific resourceregion. In one example of the present invention, if Type 0 RA of LTE isused, a specific resource region (which is referred to as an R-PDCCHsearch space) in which control information may be transmitted may berestricted to K-th RBs of allocated RBG(s). Here, K denotes an integerless than the number of RBs configuring an RBG. In this case, the K-thRBs of all allocated RBGs may transmit an R-PDCCH. K may be a first RBor a last RB of an RGB group. Even in Type 1 or 2 RA, the concept of theRBG may be used and a specific RB of an RBG may be used as a resourceregion for R-PDCCH transmission in the tautological sense.

In addition, a method of separating RB(s) for the R-PDCCH search spacefrom each other by the square of P within the RBG set if the R-PDCCHsearch space is set to one subset of an RBG set is proposed. Here, P isthe number of RBs within an RBG. For example, assuming that the numberof RBs is 32, 11 RBGs may be defined and one RBG may include three RBs(P=3). Accordingly, the RBs for the R-PDCCH search space may be placedat an interval of 3^2=9 RBs. The above-described example corresponds tothe case in which one RBG subset is used and an interval of RBs withinthe subset is the square of P if the number of RBG subsets is 2. Theinterval between subsets may be changed depending on how many subsetsare selected.

R-PDCCH/(R-)PDSCH Allocation and Demodulation

Control information is transmitted via an R-PDCCH and data istransmitted via an (R-)PDSCH. The R-PDCCH is roughly classified into twocategories. One category is DL grant (DG) and the other category is ULgrant (UG). The DL grant contains information about time/frequency/spaceresources of the R-PDSCH corresponding to data which should be receivedby a relay and information (scheduling information) for decoding. The ULgrant contains information about time/frequency/space resources of theR-PUSCH corresponding to data which should be transmitted by a relay inuplink and information (scheduling information) for decoding.Hereinafter, a method of placing DL/UL grant in a resource region of abackhaul subframe and demodulating the DL/UL grant will be described.

FIG. 15 shows an example of placing and demodulating anR-PDCCH/(R-)PDSCH. In this example, it is assumed that resources for the(R-)PDSCH are allocated using Type 0 RA (RBG unit allocation) of theLTE. However, this example is merely exemplary and is equally/similarlyapplied to even the case in which Type 1 RA (RB unit allocation) of LTEis used. Although the case in which an RBG including DL grant isallocated to a relay is shown in FIG. 15, this is merely exemplary andthe RBG including DL grant may not be allocated to the relay.

FIG. 15 shows the case in which (a) data ((R-)PDSCH) is present, (b) ULgrant is present, or (c) UL grant for another relay is present in aresource region 1-2 in the case in which DL grant of RN#1 is present ina resource region 1-1.

In FIG. 15, a determination as to which information of (a) to (c) ispresent in the resource region 1-2 may be made using RA information(e.g., RBG or RB allocation information). For example, if all RBGs areallocated to RN#1, RN#1 may interpret RA information of DL grant anddetermine whether the resource region 1-2 corresponds to (a) or (b).More specifically, if data is present in an RB or an RBG in which afirst R-PDCCH (e.g., DL grant) thereof is detected is present in theresource region X-1, RN#1 may assume that data thereof is present inresources other than resources occupied by the first R-PDCCH.Accordingly, if RA information indicates that data is present in the RBor RBG, RN#1 may determine that another R-PDCCH is not present in the RBor RBG except for DL grant. That is, the relay may determine that theresource region 1-2 corresponds to (a). If the RA information indicatesthat data is not present in the RB or RBG, the relay may determine thata second R-PDCCH is present as in (b) or (c) and detect an appropriatedata start point (e.g., a resource region 2-1). At this time, the BS andthe relay may assume that the size of the second R-PDCCH is constant. Incase of (c), by attempting CRC detection based on an RN ID, it may bedetermined that the second R-PDCCH is not UL grant for RN#1. Although RAinformation is used to distinguish among (a), (b) and (c), it may beimplicitly set that the RBG including DL grant is always resourcesallocated for data of RN#1 in advance.

Although FIG. 15 shows the case in which DL grant is present in thewhole resource region X-1 (e.g., 1-1), this is merely exemplary and theabove-described method may be equally applied to the case in which DLgrant is present in a part of the resource region 1-1. Although FIG. 15shows the case in which DL grant is present in the resource region X-1,UL grant may be present in the resource region X-1 instead of DL grant.In this case, the relay may first decode UL grant instead of DL grant.Although the second R-PDCCH is UL grant in FIG. 15, this is merelyexemplary and the second R-PDCCH may be DL grant.

FIGS. 16 to 17 show other examples of placing and demodulating anR-PDCCH/(R-)PDCCH. In this example, it is assumed that resources for the(R-)PDSCH are allocated using Type 0 RA (RBG unit allocation) of LTE.However, this example is merely exemplary and is equally/similarlyapplied to even the case in which Type 1 RA (RB unit allocation) of LTEis used. Although the case in which an RBG including DL grant isallocated to a relay is shown in FIGS. 16 and 17, this is merelyexemplary and the RBG including DL grant may not be allocated to therelay.

FIGS. 16 and 17 show the case in which (a) data ((R-)PDSCH) is presentin the resource region 2-1/2-2 (not shown), (b) UL grant for RN#1 ispresent in the resource region 2-1 (FIG. 16), or (c) UL grant for RN#1is present in a resource region 2-1/2-2 (FIG. 17), in the case in whichDL grant for RN#1 is present in the resource region 1-1/1-2.

In this case, RN#1 performs blind decoding so as to distinguish among(a), (b) and (c). Data or control information of RN#1 is preferablypresent in the resource region 2-X.

In addition, RN#1 may distinguish among (a), (b) and (c) using RAinformation (e.g., RBG allocation bit) of the DL grant. For example,RN#1 may determine whether data of RN#1 or UL grant restrictivelyallocated to the resource region 2-1 is present in the resource region2-1 using RA information (that is, (a) or (b)) (case A). In addition,RN#1 may determine whether data of RN#1 or UL grant restrictivelyallocated to the resource region 2-1/2-2 is present in the resourceregion 2-1/2-2 using RA information (that is, (a) or (c)) (case B). Thebase station-relay operation is set to one of case A or case B. That is,RN#1 may distinguish between (a) and (b) or (a) and (c) using RAinformation (e.g., RBG allocation bit). The RBG allocation bitindicating which of (a) and (b) or (a) and (c) is used is set inadvance. For example, it is assumed that UL grant is restricted to theresource region 2-1 or the resource region 2-1/2-2 in advance.

In addition, in the case in which DL grant for RN#1 is present in theresource region 1-1/1-2, (a) data of RN#1 is present in the resourceregion 2-1/2-2 (not shown), (b) DL or UL grant for another RN is presentin the resource region 2-1 (FIG. 16), or (c) DL or UL grant for anotherRN is present in a resource region 2-1/2-2 (FIG. 17). In this case, (a)and (b) or (a) or (b) may be distinguished using the RBG allocation bit.A determination as to which of (a) and (b) or (a) and (c) is used shouldbe set using the RBG allocation bit in advance.

In the above-described method, assuming that that only the same DL/ULgrant size as the DL grant size is present, the RBG allocation bit isused to determine whether the value present in the resource region 2-1or 2-1/2-2 is data or control information and the size of the DL/ULgrant (that is, the resource region 2-1 or 2-1/2-2) may be determinedaccording to the size of the detected DL grant.

The above-described method is equally applied to the case in which DLgrant is present in the resource regions 1-1, 1-2 and 1-3. Theabove-described method is equally applied to the case in which all orpart of the UL grant is present in the resource regions 1-1, 2-1 and 3-1instead of DL grant. In this case, in the above-described method, therelay first blind-decodes UL grant instead of DL grant.

Demodulation Method Using the Same DM RS Port

A method of demodulating a DL transmission signal of another resourceregion using a DM RS corresponding to a successful DM RS port ifdemodulation of grant (e.g., DL grant) for RN#1 is successful in theresource region 1-1 and, otherwise, demodulating a DL transmissionsignal of another resource region using a DM RS different from the DM RSused in the resource region 1-1 is proposed. For example, ifdemodulation of DL grant of RN#1 is successful in the resource region1-1, a DL transmission signal (e.g., UL grant) of the resource region1-2 may be demodulated using the DM RS corresponding to the successfulDM RS port and, otherwise, the DL transmission signal (e.g., UL grant)of the resource region 1-2 may be demodulated using a DM RS differentfrom the DM RS port used in the resource region 1-1. More specifically,if demodulation is successful in the resource region 1-1 using DM RSport 0, the DL transmission signal (e.g., UL grant) of the resourceregion 1-2 may be demodulated using the DM RS of the same DM RS port 0and, otherwise, if demodulation fails, decoding may be performed usingthe DM RS of DM RS port 1.

Method of Filling RB Pair with UL Grant (or DL Grant) in TDM+FDM

If UL grant of RN# is present in the resource region 1-1 (that is, if DLgrant of RN #1 is not present), the resource region 1-2 may not be used.In order to solve such a problem, a method of filling the resourceregion 1-2 with UL grant of the relay(s) including only UL grant isproposed. If a plurality of relays including only UL grant is present,it is possible to minimize resource waste by filling the resourceregions X-1 and X-2 with UL grant.

Similarly, even in the case in which only DL grant is present, a methodof allocating DL grant to the resource region 1-1 and the resourceregion 1-2 is proposed.

RS Port Allocation Method

FIGS. 18 to 19 are diagrams showing examples of dividing an RB pair intoa plurality of RE groups. In the examples of FIGS. 18 and 19, it isassumed that all or part of symbols of a subframe is defined in a startand end part of a resource region.

FIG. 18 shows the case of dividing one RB pair into two RE groups (X-aand X-b). In FIG. 18, the sizes of X-a and X-b (X=1, 2, 3) may be thesame or different. It is assumed that the resource regions 1-a and 1-bare used to forward DL grant and UL grant of RN#1, the resource region2-a is used to forward DL grant of RN#2, the resource regions 2-b and3-a are used to forward DL grant of RN#3, and the resource region 3-b isused to forward UL grant of RN#3. In this case, the resource regions 1-aand 1-b are configured to perform demodulation based on one DM RS port,the resource regions 2-a and 2-b are configured to perform demodulationbased on different DM RS ports, and the resource regions 3-a and 3-b areconfigured to perform demodulation based on the same DM RS port. By thisconfiguration, it is possible to obtain a better performance using thesame DM RS port in case of DL/UL grant forwarded to the same RN and tosuitably allocate a DM RS port to each RN in case of DL/UL grantforwarded to different RNs.

FIG. 19 shows the case of dividing one RB pair into three RE groups(X-a, X-b and X-c). FIG. 19 is equal to FIG. 18 except that the numberof RE groups is changed. Thus, for a description thereof, refer to FIG.18.

R-PDCCH Mapping and Detection in Case of High Aggregation Level

In the relay, an R-CCE aggregation level (e.g., 1, 2, 4, 8, . . . ) ofan R-PDCCH may be changed according to channel environment. This issimilar to a CCE set of an LTE PDCCH. The R-CCE is defined in order torepresent a CCE for a relay, for convenience. In the followingdescription, R-CCE and CCE are used interchangeably. It is assumed thatDL grant of the R-PDCCH is present in three RBs as shown in FIG. 20 andUL grant is transmitted in a second slot of two RB pairs. In this case,when DL grant is blind-decoded to check R-CCE aggregation shown in FIG.20, the relay may not be aware of whether UL grant or data is present inthe second slot.

A method similar to the above-described method is applicable. That is,it is possible to indicate whether UL grant is present in the secondslot using an RBG allocation bit. Preferably, it may be assumed that anRBG including DL grant is allocated to the relay. Accordingly, if DLgrant is present in a first slot, a resource allocation bit of the RBGmay indicate whether an R-PDSCH or UL grant is present in a second slot.The following cases are possible.

(a) Presence of the R-PDSCH in the second slot, or

(b) Presence of UL grant for a relay or UL grant for another relay inthe second slot. UL grant of another RN may be CRC checked using an RNID.

It is necessary to determine in which RB(s) UL grant is present. Thenumber of RB pairs including UL grant may be changed according to R-CCEaggregation level.

The number/positions of RB pairs including UL grant may be checked bygenerating a simple relationship between a DL grant size and a UL grantsize, which will be described with reference to FIGS. 21 to 22.

Referring to FIG. 21, UL grant may always be present in an RB pairincluding DL grant. Accordingly, if DL grant is present in two RB pairs,UL grant may be equally present in two RB pairs. Accordingly, if DLgrant is successfully detected, the relay may check where UL grant ispresent. At this time, the aggregation level of UL grant may be set tobe greater than the aggregation level of DL grant. Alternatively, it maybe defined that a difference between the aggregation level of DL grantand the aggregation level of UL grant is N_level in advance.

In one embodiment, it may be defined that one R-CCE is present in afirst slot of an RB pair and two R-CCEs are present in a second slot. Inthis case, the R-CCE of the first slot and the R-CCE of the second slotare different in size. According to the present example, it may bedefined that the aggregation level of DL grant×2=the aggregation levelof UL grant in advance. Referring to FIG. 21, the aggregation level ofDL grant for RN#1 is 1 and the aggregation level of UL grant is 4.Similarly, the aggregation level of DL grant for RN#2 is 3 and theaggregation level of UL grant is 6.

As another example, it may be defined that an R-CCE size may be definedin slot units. That is, one R-CCE is present in a first slot of an RBpair and one R-CCE is present in a second slot. In this case, the R-CCEof the first slot and the R-CCE of the second slot are different insize. According to this example, it may be defined that the aggregationlevel of DL grant=the aggregation level of UL grant in advance.Referring to FIG. 21, in case of RN#1, the aggregation level of DLgrant=the aggregation level of UL grant=2. Similarly, in case of RN#2,the aggregation level of DL grant=the aggregation level of UL grant=3.

Referring to FIG. 22, an R-CCE size is set to 1 and the aggregationlevel of DL grant is equal to the aggregation level of UL grant. Forexample, the R-CCE size may be 32 REs. In this case, since the resourceregion of the second slot is larger, the placement shown in FIG. 22 isobtained. In case of RN#2, only some resources of the second slot of thesecond RB pair are used to transmit UL grant. In this case, an emptyspace of the second slot may be used to transmit data (FIG. 22( a)) ormay not be used to transmit data (FIG. 22( b)).

As another method, the number of RBs occupied by UL grant may berestricted. For example, as in the case of RN#1 of FIG. 22, there is arestriction that UL grant may always be transmitted in the second slotof one RB pair. Such a restriction may be fixed in the standard and maybe transmitted from a BS to an RN through a higher layer signal. If sucha restriction is present, the RN may easily check the position of theregion occupied by UL grant by reinterpreting the above-described RAinformation and thus check the position of a data signal.

In the above description, the RBG allocation bit may be reinterpretedand used to distinguish between UL grant and data (R-PDSCH) because ofthe assumption that the RBG is used only for the RN. However, if the RBGis used as original meaning thereof, a separate signal may be generated.Such a signal may be present in the R-PDCCH. A determination as towhether a separate signal is used or the RBG is reinterpreted and usedmay be set in advance or may be configured through semi-staticsignaling.

If decoding of UL grant fails in spite of indicating that UL grant ispresent in the above-described methods, data (including UL grant)present in the slot may be combined with data retransmitted via HARQ. Inthis case, since serious error may be generated in HARQ-combined datadue to UL grant, previous data which may be included in UL grant may notbe used in a HARQ combining process.

FIG. 23 shows a method of enabling DL grant to indicate presence of ULgrant in a second slot by locating DL grant in a first slot even whenonly UL grant is present.

Referring to FIG. 23, even in the case in which there is no downlinkdata (e.g., (R-)PDSCH) to be transmitted from a BS to an RN (that is, ULgrant only case), null DL grant (or dummy DL grant) may be transmittedin order to inform the RN that UL grant is present in the second slot ofthe same RB pair. According to the present example, regardless ofpresence/absence of downlink data for the RN, blind decoding for ULgrant may be omitted and thus blind decoding complexity of the RN isreduced. In the case in which both DL grant and UL grant are transmittedbut there is no downlink data for the RN as in this example, it shouldbe indicated that there is no data corresponding to DL grant (that is,null DL grant). Therefore, null DL grant may indicate that all downlinktransport blocks or codewords are disabled. In addition, null DL grantmay indicate that a downlink transport block size (TBS) is TBS=0 orTBS<K (e.g., 4 RBs). In addition, null DL grant may indicate that thereis no RB allocated for downlink transmission. In addition, a specificfield within null DL grant may be set to “0” or “1”. If null DL grant isdetected, the relay interprets that data corresponding to null DL grantis not transmitted and checks presence of UL grant in the second slotfrom null DL grant.

Method of Indicating Use State of Second Slot (e.g., RA Bit Use)

Hereinafter, a method of indicating presence/absence of UL grant orpresence/absence of an (R-)PDSCH using a bit (or similar information) ofa DCI resource allocation (RA) field so as to accurately perform PDSCHdata decoding will be described. For convenience, resource allocationtechnology used in the description is LTE technology. An RA bitindicates whether an RB or an RBG is allocated for PDSCH transmission.It is assumed that the RB or RBG is not allocated for (R-)PDSCHtransmission in case of RA bit=0 and is allocated for R-PDSCH in case ofRA bit=1. The meaning of the RA bit may be inversely interpreted. Themeaning of the RB bit may be differently interpreted according to DLgrant and UL grant.

DL grant and UL grant may be present in RBs of different slots. Forexample, DL grant may be present in an RB of a first slot and UL grantmay be present in an RB of a second slot. In this case, a resourceregion for DL data and a region for UL grant coexist. Resources used toactually transmit DL data are indicated by RA of DL grant and resourcesused to actually transmit UL grant are checked blind decoding.Accordingly, if UL grant is detected in a resource region to which DLdata is allocated, an RN receives/decodes DL data from resources otherthan resources in which UL grant is detected (that is, rate matching).For this reason, non-detection or misdetection of UL grant unpreferablyinfluences on DL data decoding.

In order to solve this problem, the following restrictions areapplicable to BS-RN communication.

-   -   The RN may assume that there is no UL grant in an RB or RBG in        which a DL RA bit is set to 1. That is, the RN may assume that        UL grant may be transmitted only in an RB or RBG in which a DL        resource allocation bit is 0. In this example, some resources        may be used to transmit data in an RBG in which a DL resource        allocation bit is 0.    -   The above restriction may guarantee accurate rate matching upon        DL data (that is, (R)-PDSCH) decoding even when UL grant        detection fails (that is, a non-detection case) or UL grant is        misdetected (that is, a false alarm case).

Accordingly, the BS does not transmit UL grant in an RB or RBG in whicha DL resource allocation bit is set to 1. For example, in case of Type 0RA, the BS does not transmit UL grant in an RBG to which DL data for theRN is allocated, except for an RBG in which DL grant and UL grantcoexist.

FIG. 24 is a diagram showing the case of transmitting UL grant only inthe case in which a DL RA bit is set to 0. For convenience, this exampleis described using Type 0 RA of LTE. RA=1 means that an RBG is allocatedfor DL data transmission according to normal RA interpretation. However,RA=0 may have meaning different from normal RA interpretation. In thisexample, it is assumed that a DL grant search space and a UL grantsearch space are respectively present.

Referring to FIG. 24, if DL grant is successfully detected and an RA bitis, for example, “0”, UL grant may be designed to be present at anarbitrary place of an RB or RBG in which the RA bit is “0” within a ULgrant search space (UL SS). Although the UL grant search space isconfigured regardless of the RA bit, a BS scheduler may intentionallyallow UL grant to be present only in a place where an RA bit is “0”.That is, RA bit=0 means an RBG in which UL grant may be transmitted andresources in which UL grant may be transmitted may be restricted toresources satisfying both UL SS and RA bit=0. In this case, RA bit=0indicates some subsets in an R-PDCCH search space. Accordingly, the RNmay restrict a UL grant search position to resources set to RA bit=0within the UL SS if DL grant is detected. Therefore, it is possible toprevent unnecessary UL grant misdetection. In other words, an RB or RBGwith RA bit=1 may be excluded from a UL grant search space.

If RA bit=1, the RN may assume that UL grant is not transmitted in theRB or the RBG. In contrast, RA bit=0, the RN may assume that UL grantmay be transmitted in the RB or RBG. The BS transmits UL grant in the RBor RBG with RA bit=0. The RN may perform blind decoding when beingunaware of presence/position of UL grant and decode UL grant at aspecified position when being aware of the position of UL grant.According to interpretation of RA bit=0, since a UL Grant search space(UL SS) can be dynamically restricted (or allocated) using DL RA, it ispossible to reduce the number of times of blind decoding for UL grant.

In the above description, RA bit=0 is interpreted as resources used totransmit UL grant. However, RA bit=0 may mean an RB or RBG in which ULgrant is actually transmitted within UL SS. In this case, interpretationof RA bit=0 may be restricted to a specific RB (pair) or RBG. Forexample, interpretation of RA bit=0 may be restricted to an RB (pair) orRBG in which DL grant is present.

In consideration of data transmission, interpretation of RA bit=0 mayfurther include the following cases. For example, an RBG with RA=0 mayinclude data transmission if DL grant or an arbitrary R-PDCCH is presentin the RBG ((a) to (b)). As another example, there may not be datatransmission in an RBG with RA=0 regardless of presence/absence of anR-PDCCH ((c) to (d)).

In FIG. 24, a dotted line shows the case in which Type 1 RA is used. InType 1 RA, interpretation of an RA bit is applied in RB units.

In the following description, if an aggregation level of DL and UL grantis increased, it is assumed that R-PDCCHs are sequentially andcontiguously extended and allocated to neighboring VRBs(non-interleaving). In this case, R-PDCCHs are not non-contiguouslyallocated. Actual PRB mapping may be different. Although RA informationwithin DL grant is described based on Type 0 of LTE in the followingdescription, the RA information within DL grant is not limited to aspecific type in the present invention.

FIG. 25 shows a method of indicating an RA state (e.g., presence/absenceof UL grant) of a second slot according to the present invention. FIG.25 shows the case of RBG=3RBs, 1 CCE DL grant and 1 CCE UL grant. Forconvenience, one RBG, in which DL grant is present, among three RBGsallocated by DL RA is shown. If interleaving is applied, DL grant may bepresent in a plurality of RBs or RBGs.

Referring to FIG. 25, if 1-CCE DL grant is transmitted, a method ofindicating whether UL grant is present in a resource region of a nextslot is performed by reinterpreting the existing RA bit (an RB indicatoror an RBG indicator). For example, in case of RA bit=0, UL grant may bepresent in a next slot of an RB pair in which DL grant is present in theRBG and an R-PDSCH is allocated from a next RB pair. In contrast, incase of RA bit=1, UL grant is not present in a next slot of an RB pairin which DL grant is present in the RBG and the resource region isfilled with an R-PDSCH or an R-PDSCH is not present in the resourceregion. Presence/absence of the R-PDSCH is set in advance as shown inFIG. 24. Interpretation of the RB bit shown in FIG. 25 may be restrictedto an RB (pair) or RBG in which DL grant is present.

In LTE, DCI formats 0 and 1A are equal in size and are distinguishedusing a 1-bit type indication field. If DL grant and UL grant arerespectively configured in independent spaces, a field fordistinguishing DL/UL grant is not necessary. Accordingly, although notshown, as another example, a type indication field for distinguishingbetween DCI formats 0 and 1A may be used as described above. Forexample, a type indication field may indicate presence/absence of ULgrant or presence/position/placement of UL grant (e.g., a second slot ofan RB pair in which DL grant is present, 1 CCE). In this example, thetype indication field may be used additionally to or independently ofthe existing RA bit.

Since a resource region of a second slot is greater that a resourceregion of a first slot within an RB pair, the number of CCEs included inan RB of each slot may be differently defined. For example, the RB ofthe first slot may include one CCE and the RB of the second slot mayinclude two CCEs. In this case, UL grant may occupy only one CCE betweentwo CCEs of the second slot. In addition, UL grant may be predeterminedor signaled so as to completely fill the resource region of the secondslot (2 CCEs). The CCE aggregation level of UL grant is preferablyextended to 2, 4 or 6 because of simple signaling.

FIGS. 26 a to 26 c show UL grant transmission according to a DL grantCCE aggregation level. FIGS. 26 a to 26 c show the cases in which the DLgrant CCE aggregation level is 1, 2 and 3, respectively. AlthoughRBG=3RBs is shown, the number of REs configuring the RBG is not limitedthereto. For convenience, one RBG, in which DL grant is present, amongthree RBGs allocated by DL RA is shown. If interleaving is applied, DLgrant may be present in a plurality of RBs or RBGs.

Referring to FIG. 26 a, if 1-CCE DL grant is detected by blind decoding(BD), it is important to check how UL grant is placed in a secondslot/resource region of an RB pair in which DL grant is detected. Ifdecoding of UL grant fails and this UL grant is misrecognized as dataand is decoded, (R-)PDSCH decoding error may be generated. Accordingly,it is necessary to accurately detect the position of UL grant in termsof error case handling. If 1-CCE DL grant is detected in a firstresource region, a method of indicating UL grant or (R-)PDSCH (includingempty) in a second resource region may use an RA bit (RB indicator) foran RB or an RA bit (RBG indicator) for an RBG. Since only two cases areindicated, 1-bit information is sufficient.

Referring to FIG. 26 b, if 2-CCE DL grant is detected, the number ofcases of placing UL grant and R-PDSCHs in a second resource region of anRB pair is large, but may be restricted to three if theabove-description assumption is applied as shown. Accordingly, insteadof 1 bit, a 2-bit indication is required. All cases may be indicated byadding additional 1 bit to the 1-bit RBG indication of FIG. 26 a. Theadditional 1 bit may be obtained from a DCI format. For example, in aDCI field, a bit left by reducing the size of a field which may berestricted in backhaul may be used. More specifically, if a field isused in backhaul, a method of slightly reducing the width of theexisting RA information and using the remaining bit may be used. In anLTE-A DCI format, a bit of a field, significance of which is not presentor is reduced with respect to backhaul, in an additionally defined fieldof an LTE-A DCI may be borrowed and used. For example, a CIF field has 3bits, but a maximum number of carriers in LTE-A is 5 and the number ofactually used carriers may be less than the maximum number of carriers.Accordingly, 1 bit or a plurality of states may be borrowed from the CIFfield. In addition, a combination of RRC signaling and an RA bit may beused. More specifically, the number of cases may be partially restrictedthrough RRC signaling and one of the remaining cases may be indicated byan RA bit. For example, a UL grant transmission case may be restrictedto (a) and (c) through RRC signaling and (a) or (c) may be indicated byan RA bit. The above description is commonly applied to all subsequentfigures.

Referring to FIG. 26 c, if 3-CCE DL grant is detected, the number ofcases of placing UL grant and R-PDSCHs in a second resource region of anRB pair is large, but may be restricted to four if the above-descriptionassumption is applied as shown. Accordingly, as shown in FIG. 26 b, allcases may be indicated by 1 bit+1 bit=2 bits. Alternatively, 3-CCE DLgrant allocation may not be performed. By restricting a CCE aggregationlevel to 2^n (n=0, 1, 2, . . . ), it is possible to reduce DL grant BDcomplexity. For example, the RN may perform BD only with respect to 1-,2- or 4-CCE DL grant.

FIGS. 27 a to 27 d show UL grant transmission according to a DL grantCCE aggregation level if an RBG includes four RBs. FIGS. 27 a to 27 dshow the case in which the DL grant CCE aggregation level is 1, 2, 3 and4, respectively. For convenience, one RBG, in which DL grant is present,among three RBGs allocated by DL RA is shown. If interleaving isapplied, DL grant may be present in a plurality of RBs or RBGs. Sincethe basic conditions are equal to FIGS. 27 a to 27 c, refer to FIGS. 27a to 27 c, for detailed description thereof.

Referring to FIG. 27 a, if 1-CCE DL grant is detected, two transmissioncases may be applied and may be indicated by an RA bit (1 bit) of anRBG. Referring to FIG. 27 b, if 2-CCE DL grant is detected, threetransmission cases may be applied and indicated by 2 bits. As describedwith reference to FIG. 26 b, three cases may be indicated by addingadditional 1 bit to the RA bit (1 bit) of the RBG. For example, theadditional 1 bit may be obtained from a DCI format. For example, a bitleft by slightly reducing the width of the existing RA information maybe used. In addition, 1 bit or a plurality of states may be borrowedfrom the CIF field. In addition, a combination of RRC signaling and anRA bit may be used. In this case, the number of cases may be restrictedthrough RRC signaling and one of the remaining cases may be indicated byan RA bit.

Referring to FIG. 27 c, if 3-CCE DL grant is detected, four transmissioncases may be applied. Accordingly, all cases may be indicated by 2 bits.Similarly to RBG=3RBs of FIG. 26 c, the 3-CCE DL grant case may beexcluded. Referring to FIG. 27 d, if 4-CCE DL grant is detected, fivetransmission cases may be applied. Accordingly, all cases may not beindicated by 2 bits. However, an additional assumption may be given. Forexample, in FIG. 27 d, 3-CCE UL grant (c) in which the CCE aggregationlevel is an odd number may not be used. Alternatively, in FIG. 27 d,4-CCE UL grant may not be used. Since resources of the second slot aremore than resources of the first slot, the CCE aggregation level of DLgrant may be set to be lower than the CCE aggregation level of UL grant.By excluding one or more cases from (a) to (d), all cases may beindicated by 2 bits.

In the above-described case, all cases may be indicated by 2 bits byrestricting the UL grant aggregation level. For example, the UL grantaggregation level may be restricted to 1 and 2 or 1, 2 and 4. Inparticular, since a second resource region in which UL grant is locatedis large, it is assumed that only 1 RB (e.g., 1-CCE) or 2 RBs (2-CCE) isused. Since the CCE of the second slot includes REs which correspond toabout twice those of the CCE of the first slot, even when the UL grantaggregation level is restricted to 1 or 2, UL grant may substantiallyhave a code rate corresponding to DL grant of an aggregation level of 2or 4. If a boundary between the first resource region and the secondresource region is adjusted such that the resource regions areidentical, a method of setting the UL grant aggregation level to 1, 2and 4 is advantageous. In this case, the DL grant aggregation ispreferably restricted to 1, 2 and 4.

CCEs having the same size may be defined or several CCE having arestricted size may be defined. The above-described CCE conceptuallyrepresents a unit for allocating DL/UL grant as shown in each figure.

In the above description, an example of providing information about ause state (e.g., presence/placement of UL grant) of a second slot wasdescribed by differently interpreting the RA bit. However, instead ofdifferently interpreting the RA bit, a new bit field may be added to DCIin order to provide information about the use state of the second slot.The new bit field may be part (e.g., 2 bits) of a bit field previouslydefined for another purpose or a dedicated bit field newly defined forthis purpose.

FIG. 28 shows an example of using a field of a DCI format in order toprovide information about a use state (e.g., presence/placement of ULgrant) of a second slot. The method of FIG. 28 may be used along with orseparately from interpretation of the RA bit.

Referring to FIG. 28, DCI format 0/1A includes a 1-bit flag field (0/1A)for distinguishing the DCI format 0/1A. DCI format 0 is for UL grant andDCI format 1A is for DL grant. As shown in the above figures, ifresources used to transmit DL grant and UL grant are divided in a timedomain or a UL grant size is different from a DL grant size, the flagfield for distinguishing the DCI format 0/1A is not necessary.Accordingly, the flag field for distinguishing the DCI format 0/1A maybe used to provide information about the use state (e.g.,presence/placement of UL grant) of the second slot. In addition, DCIformat 1A/1B/1C includes an L/DVRB indication field (L/DVRB). In case ofan RN, if DVRB is always disabled (OFF) and only LVRB is supported, theL/DVRB indication field may be used to provide information about the usestate (e.g., presence/placement of UL grant) of the second slot. DCIformat 1/2/2A/2B includes a resource allocation header field RA Hdrindicating RA type 0/1. If the RA type is semi-statically signaled by ahigher layer (e.g., RRC), a field indicating the RA type may be used toprovide information about the use state (e.g., presence/placement of ULgrant) of the second slot.

RRC Signal+RBG Indication

Next, a method of using an RRC signal in order to provide informationabout the use state (e.g., presence/placement of UL grant) of the secondslot will be described in detail. A method of maintaining each field ofthe existing DCI format and indicating information associated with a DLgrant aggregation level or a UL grant aggregation level through RRC maybe used. In particular, information associated with the DL/UL grantaggregation level may be transmitted on a RN-specific basis. Since eachRN has unique channel quality and a channel is not rapidly changed dueto the nature of backhaul, at least the aggregation level may besignaled through RRC. Information associated with the aggregation levelmay mean a DL/UL grant aggregation level (e.g., 1 CCE, 2 CCEs, etc.) oreven a resource region (or resource placement) occupied by DL/UL grant.The existing RA bit (e.g., an RBG indication bit) may be reinterpretedand used. By using the RRC signal and reinterpretation of the RA bit, aspecific bit does not need to be borrowed from the existing DCI format.For example, a CCE aggregation level may be indicated by the RRC signaland presence/absence of UL grant, presence/absence of data, etc. may beindicated by a DL RA bit in a second slot. This has an advantage thatpresence/absence of UL grant or (R-)PDSCH is dynamically indicated on asubframe basis.

FIG. 29 shows an example of indicating placement of UL grant by an RRCsignal. FIG. 29 shows the case of RBG=4RBs and 4-CCE DL grant. AlthoughFIG. 29 shows a total of five UL grant placement combinations, there maybe more various combinations. If the number of UL grant placementcombinations is restricted to 5, 5 pieces of placement information maybe signaled to each RN through RRC. The RA bit (that is, RBG indicationbit) may be used to check presence/absence of UL grant in the RBG. Forexample, if one of (a) to (d) is indicated through RRC signaling, the RNmay interpret the use state of the second slot as (a) or (e) by the RAbit. If the size of the RRC signaling bit is not problematic, placementof all cases may be signaled. Thus, optimized resource allocation ispossible. In this case, if the relay may attempt to perform blinddecoding with respect to (a) to (d) in the RBG if the RA bit is 0. Asanother method, along with or separately from interpretation of the RAbit, placement of actually transmitted UL grant may be indicated usingthe DCI field (or bit) (e.g., a type indication bit) described withreference to FIG. 28.

FIG. 30 shows all cases in which UL grant may be placed in case ofRBG=3RBs and 2-CCE DL grant. Similarly to FIG. 29, a UL grant positionis restricted using an RRC signal and presence/absence of UL grant maybe checked using an RBG indication bit.

FIG. 31 shows all cases in which UL grant may be placed in case ofRBG=1RB and 1-CCE DL grant. Unlike FIGS. 29 to 30, FIG. 31 shows thecase in which a UL grant allocation unit is decreased. FIGS. 29 to 30show the case in which one CCE is present in the RB of the second slot,and FIG. 31 shows the case in which two CCEs are present in the RB ofthe second slot. Even in this case, similarly to FIG. 29, a UL grantposition is restricted using an RRC signal and presence/absence of ULgrant may be checked using an RBG indication bit.

Although an RRC signal is an RN-specific signal in the abovedescription, the RRC signal may be defined as an RN-common signal. Thisis possible if an RN-common channel is present. In addition, theRN-common signal is preferable if the channel properties of all RN-BSlinks are substantially similar.

RA Bit Interpretation

FIG. 32 shows more various methods of RA bit interpretation. Referringto FIG. 32, the following four methods may be considered with respect toRA bit interpretation (Alt#1 to Alt#4).

Method #1 (Alt#1)

-   -   An RB pair which does not include DL grant (or a frequency        domain) in an RBG in which DL grant is detected is always used        for data (e.g., (R-)PDSCH) transmission of an RN which is a        destination of DL grant.    -   An RA bit of an RBG indicates usage of a second slot in an RB        pair including DL grant. As shown in FIG. 32, UL grant may be        transmitted in the resource region (UL grant/empty) if the RA        bit is 0 and data may be transmitted in the resource region if        the RA bit is 1. The RA bit may be inversely interpreted. In        some cases, it may be assembled that UL grant may always be        transmitted in the second slot of the RB pair including DL grant        if the RA bit is 0.

Method #2 (Alt #2)

-   -   An RB pair which does not include DL grant (or a frequency        domain) in an RBG in which DL grant is detected is not always        used for data (e.g., R-PDSCH) transmission of an RN which is a        destination of DL grant.    -   An RA bit of an RBG indicates usage of a second slot in an RB        pair including DL grant. As shown in FIG. 32, UL grant may be        transmitted in the resource region (UL grant/empty) if the RA        bit is 0 and data may be transmitted in the resource region if        the RA bit is 1. The RA bit may be inversely interpreted.

Method #3 (Alt #3)

-   -   Resources of a second slot in an RB pair including DL grant in        an RBG in which DL grant is detected are not always used for        data transmission of an RN which is a destination of DL grant.    -   An RA bit of an RBG indicates usage of a second slot in an RB        pair (or the frequency domain) which does not include DL grant.        As shown in FIG. 32, data is not transmitted in the resource        region if the RA bit is 0 and data is transmitted if the RA bit        is 1. The RA bit may be inversely interpreted.

Method #4 (Alt #4)

-   -   An RA bit of an RBG indicates usage of the resource region        except for DL grant in the RBG in which DL grant is detected.    -   As shown in FIG. 32, data is not transmitted in the resource        region if the RA bit is 0. In this case, a second slot of an RB        pair in which DL grant is present may be used to transmit UL        grant. If the RA bit is 1, data is transmitted in the whole        resource region except for DL grant within the RBG. The RA bit        may be inversely interpreted.

The method of FIG. 32 may be independently used and may be set by ahigher layer (e.g., RRC) signal or a physical layer signal. In addition,fallback may be performed using a specific method according to afrequency domain occupied by DL grant. For example, if the number of RBpairs occupied by DL grant is equal to or greater than a predeterminedvalue (e.g., 3), an operation may be performed using one previouslyselected from between method #1 and method #2 (that is, fallback mode).In addition, a method may be selected and used according to atransmission mode, whether or not interleaving is performed (that is, aninterleaving mode or a non-interleaving mode), an R-PDCCH RS type (e.g.,a DM RS or a CRS). In this case, a basic method is set as in a fallbackoperation and a specific method may be automatically applied accordingto configuration mode.

In Methods #1 to #4 of FIG. 32, a signal for distinguishing between 0and 1 may be an RA bit. As another example, in methods #1 to #4, asignal for distinguishing between 0 and 1 may be some bits (e.g., seethe description of FIG. 28) within the DCI. As another example, inmethods #1 to #4, a signal for distinguishing between 0 and 1 may be anRRC bit. As another example, in methods #1 to #4, a signal fordistinguishing each state may be an indicator of a new format composedof an RA bit and an RRC bit. For example, four states may be indicatedby combining 1 RA bit+1 RRC signal bit. In this case, an additionalstate may be defined with respect to each method. In addition, inmethods #1 to #4, a signal for distinguishing each state may be a 2-bitsignal composed of an RA bit+an additional bit (e.g., a type indicationbit, etc.).

In FIG. 32, the position of UL grant means UL grant or an empty state.If UL grant decoding fails, a corresponding region is not used for datatransmission, UL grant transmission is not different from the emptystate upon (R-)PDSCH decoding, from the viewpoint of the RN. However,from the viewpoint of the BS, there is a difference between transmissionof UL grant and non-transmission of UL grant. Accordingly, denotation ofthe figure may be changed according to viewpoint.

In FIG. 32, it is assumed that the size of DL grant (an aggregationlevel or a resource region) and the size of UL grant are identical. FIG.32 is merely exemplary and the same method is applied to the case inwhich the DL grant aggregation level and the UL grant aggregation levelare different. In this case, there are more cases with respect to eachmethod and thus a signal of 2 bits or more may be necessary.

RA Bit Interpretation Considering Asymmetric or Symmetric SubframeAllocation

FIGS. 33 to 34 show the case in which a pair of DL grant and UL grant isalways present and the case in which DL grant and UL grant areseparately present. Referring to FIGS. 33 to 34, the following sixmethods may be considered with respect to RA bit interpretation (Alt#5to Alt#10). An RA bit (or another bit or a new bit) may be used toindicate the position/placement of DL/UL grant and data.

In Method #5 (Alt #5), it is assumed that DL grant is detected in two RBpairs (e.g., aggregation level=2) and UL grant is transmitted in asecond slot (e.g., aggregation level=2) of two RB pairs. In this case,an indication bit (e.g., an RA bit) of 0 means that data is not presentin the remaining resource region of the RBG and an indication bit (e.g.,an RA bit) of 1 means that data is present in the remaining resourceregion of the RBG.

Method #6 (Alt #6) and Method #7 (Alt #7) may be applied to the case inwhich only DL grant is present, that is, the case in which UL grant isnot present. Method #6 means that up to a second slot of an RB pair inwhich DL grant is present is filled with data if an indication bit(e.g., an RA bit) is 1. In contrast, Method #7 (Alt #7) indicates thatdata is not present in a second slot of an RB pair in which DL grant ispresent if an indication bit (e.g., an RA bit) is 1 and data is presentonly in the remaining RB pair in which DL grant is not present. InMethod #6/#7, if an indication bit (e.g., an RA bit) is 0, it means thatdata is not present in resources except for resources in which DL grantis present within the RBG.

Method #8 (Alt #8), Method #9 (Alt #9) and Method #10 (Alt#10) of FIG.34 show the case in which the aggregation levels or the resource regionsof DL grant and UL grant are not identical. Although the DL and UL grantaggregation levels are identical due to a single CCE size, DL grant maybe placed in two RBs and UL grant may be placed in one RB. In this case,this example means RB mapping rather than aggregation level.

The above-described RA interpretation method may be differently appliedaccording to backhaul subframe allocation. For example, if a pair of aDL subframe and an UL subframe is allocated to backhaul (that is, ULgrant for UL backhaul is transmitted in a DL backhaul subframe), RAinterpretation is applicable on the assumption that UL grant is alwaystransmitted, as in method #5 or #8. In contrast, in a DL subframe whichdoes not accompany a UL subframe in which UL grant will be transmittedon a HARQ timeline (which may be referred to as a DL standalonesubframe), RA interpretation may be applied on the assumption that ULgrant is not present as in Methods #6, #7, #9 and #10. That is,according to the present method, the signal 0/1 may be interpreted inthe subframe in which DL grant and UL grant are present and the DLstandalone subframe. For example, even when there is no separate signal,the RN may automatically apply interpretation of Methods #5 and #8 in anormal subframe and interpretation of Methods #6, #7, #9 and #10 in theDL standalone subframe.

RA Interpretation Considering Various Aggregation Levels

FIG. 35 illustrates the role of an RA bit in a blind decoding process ifthe aggregation levels of DL grant and UL grant are changed.

Referring to FIG. 35, if the RA bit is 1, it indicates that the RBG iscomposed of only DL grant and (R-)PDSCH data. That is, a place exceptfor an RB in which DL grant is detected through blind decoding is filledwith data to be transmitted. If the RA bit is 0, it indicates that ULgrant is necessarily present. The aggregation level of UL grant may bechecked through blind decoding. That is, if blind decoding of DL grantis successful, RA bit=0 or RA bit=1 is applied to the region except forthe RB. In case of RA bit=0, the RN may check the region occupied by ULgrant through blind decoding. Accordingly, if only one RB is occupied byUL grant through blind decoding, the remaining region is filled withdata to be transmitted. Similarly, if UL grant extends over a pluralityof RBs, the region except for the RBs, in which UL grant is present,obtained through blind decoding is used as data. However, if the numberof RBs over which DL grant extends is greater than the number of RBsover which UL grant extends, the region except for the region in whichDL grant is transmitted in a first region may be empty. That is, whenonly UL grant is transmitted in a second slot within an RB pair, a firstslot of the RB pair may be always empty. That is, resources of a firstslot within the RB pair in which UL grant is transmitted may be usedonly for DL grant and may not used for data.

Even when the RA bit is 0, blind decoding of UL grant in the second slotmay fail. In this case, the RN should decode data in a state of beingunaware of up to which region UL grant is present and thus data decodingmay fail. Since blind decoding failure of UL grant does not frequentlyoccur, data decoding may be abandoned. That is, if UL grant decodingfails, data may be discarded.

FIG. 36 illustrates the role of an RA bit in a blind decoding process inthe case in which it is assumed that DL grant and UL grant are alwaystransmitted.

Referring to FIG. 36, the case in which the RA bit is 1 does not occurin FIG. 35. Although UL grant is present, since it is impossible toguarantee that the UL and DL grant aggregation levels are identical, thefour cases in which the RA bit is 0 in FIG. 35 are valid. Accordingly,in the present example, the RA bit may be used to divide the cases inwhich the RA bit is 0 into two groups in FIG. 35. For example, the casein which the RB occupied by UL grant is equal to or greater than the RBoccupied by DL grant is indicated by RA bit=0 and the opposite casethereof is indicated by RA bit=1. In case of RA bit=1, a combination ofDL grant and data may always be present in at least one RB pair. Adetermination as to over how many RBs UL grant extend (that is, anaggregation level) may be made by blind decoding. Accordingly, if blinddecoding of UL grant fails, a method of discarding data of RBG may beused. If an additional bit (e.g., a type indication bit) is used, allfour cases may be distinguished (RA bit+type bit=2 bits). Accordingly,it is possible to detect UL grant without blind decoding. Meanwhile, ifthere is a restriction in placement of DL grant and UL grant, a 1 bitmay be signaled without an additional bit. For example, two cases amongthe cases shown in FIG. 36 may be excluded by restricting a size ratioof DL grant and UL grant or restricting an aggregation level.

Signaling Indicating One of Resource Use Methods

FIG. 37 shows an example of a resource use method of a second slot. Forconvenience, FIG. 37 shows Method #1 to Method #4 shown in FIG. 32.Accordingly, for Method #1 to Method #4, refer to FIG. 32.

Method #1 (Alt #1) will be briefly described with reference to FIG. 37.In Method #1, if DL grant is present, data thereof is always present.Here, it is assumed that the size of UL grant is decided according tothe size of DL grant. For example, it may be assumed that the size of ULgrant is equal to or less than the size of DL grant, in terms of thesize of the actual resource region or the CCE aggregation level. Method#1 is preferable in terms of resource use and UL grant decoding errorcase handling. However, in some cases, Method #4 or Method #3 may beadvantageous when taking RS format and interleaving into consideration.Accordingly, a method of selecting and using each method according tocircumstances is proposed. For example, both Method #1 and Method #4 maybe used and signaling (e.g., RRC) for distinguishing between bothmethods may be used. If DL grant is transmitted in several RBGs, thereis an assumption/restriction that an assumption that RBs in which DLgrant is not included in one RBG are used as data is equally applied toall RBGs. Otherwise, whenever the RBG is increased by one, additionalsignaling information of 1 bit is required. The restriction in thenumber of bits is not problematic in case of RRC signaling.

As another example, Methods #1, #3 and #4 may be configured,respectively. Method #3 may be used if interleaving is applied. In caseof interleaving, a resource region is not used to transmit dataregardless of whether or not part of UL grant is present in the secondslot. Accordingly, if interleaving is applied, Method #3 is preferablyused. In addition, a method of automatically determining a methodaccording to a transmission mode may be used. In addition, each methodmay be selected and used depending on whether interleaving is applied(that is, an interleaving mode or a non-interleaving mode) or an R-PDCCHRS type (e.g., a DM RS or a CRS). In this case, a basic method is set asin a fallback operation and a specific method may be automaticallyapplied according to configuration mode.

Association Between DL/UL Grant DCI Formats

DL/UL grant DCI formats which may be transmitted together via one RBpair may be restricted in consideration association therebetween.Association may be set according to various criteria, for example, usinga DCI format size. For example, if DCI format 1 is used in DL grant, DCIformat 0 is used in UL grant and, if DCI formats 2 and 2x are used in DLgrant, DCI format 3 (new UL MIMO format) may be used in UL grant.Therefore, it is possible to substantially equally maintain the size ofDL grant and the size of UL grant. In particular, since the resourceregion of the second slot in which UL grant is present is large, thesize of UL grant does not exceed the size of DL grant.

Error Case Handling

FIG. 38 shows an error case handling method in FIG. 29.

Referring to FIG. 38, presence/absence of data is indicated using 1 RAbit and blind decoding is performed with respect to UL grant. In thiscase, in order to accurately indicate the size of UL grant, anadditional bit (L1/L2, RRC signaling) may be used.

FIGS. 39 to 40 show error case handling methods with reference to FIG.35.

Referring to FIG. 39, if a DL grant size is M, the number of cases forplacing UL grant may be restricted by setting a UL grant size N to beless than M. For example, if a UL grant size is set to 2 (=N) or less(that is, 1 or 2) when a DL grant size is 3 (=M), it is possible toreduce blind decoding complexity. More specifically, as shown, assumingthat an aggregation level of UL grant is 2 CCEs or less when anaggregation level of DL grant is 3 CCEs, the number of cases isdecreased using (c) or (d) among (a) to (d) when a signaling or RB bitis 0. Thus, it is possible to reduce blind decoding complexity.

FIG. 40 shows the case where a transmitter and a receiver promise toexclude the case in which a signaling bit (e.g., an RA bit) is 1 (leftfigure) in FIG. 39 in addition to restriction of the UL grant sizedescribed with reference to FIG. 39. In this case, since a relaydistinguishes between only two cases (that is, (c) and (d)), a 1-bitindication is possible. In other words, it is assumed that, when a DLgrant size is M, a UL grant size N should be less than M and the numberof cases for placing UL grant is restricted to two. For example, if a ULgrant size is less than 2 (=N) when a DL grant size is 3 (=M) (that is,1 or 2), a 1-bit indication is possible.

Support of “DL Grant Only Case” and “DL Grant+UL Grant Case”

FIGS. 41 and 42 show other rules for placing an R-PDCCH/data. Inparticular, if DL grant and UL grant are simultaneously present, Method#5 (Alt #5) and Method #8 (Alt #8) may be applied and, if only DL grantis present (that is, UL is not present), Method #6 (Alt #6), Method #7(Alt #7), Method #9 (Alt #9) and Method #10 (Alt #10) may be applied.Two cases will be described as follows:

(a) Case in which DL grant is present and UL grant is always present

(b) Case in which only DL grant is present and UL grant is not present

Method #5 (Alt #5) and Method #8 (Alt #8) are used in case of (a) andMethod #6 (Alt #6), Method #7 (Alt #7), Method #9 (Alt #9) and Method#10 (Alt #10) are used in case of (b). Assuming that (a) and (b)coexist, a set is defined in advance such that one of the methodsapplied to (a) is used in a specific subframe in which (a) occurs andone of the methods applied to (b) is used in a specific subframe inwhich (b) occurs, and is configured through signaling. For example,placement of R-PDCCHs and data is checked according to Method #5 in caseof (a) and placement of R-PDCCHs is checked according to Method #6 incase of (b). At this time, Method #5 and Method #6 may be grouped to oneset and may be configured through signaling. As another method, Mode 1using only (a) and Mode 2 using both (a) and (b) may be set andconfigured through signaling. In general, in consideration of symmetricsubframe allocation, a possibility wherein (a) occurs is high. In a TDDstructure, (b) may frequently occur. In addition, a method of using bothMode 1 (e.g., Method #5) and Mode 2 (e.g., Methods #5 and Method #6) maybe used. Mode 1 and Mode 2 may be automatically applied according tosubframe type. The subframe may be implicitly checked according to asubframe allocation pattern or a subframe index. If various methods areapplied (e.g., Mode 2—Method #5 and Method #6) in one mode, Method #5and Method #6 may be distinguished in Mode 2 depending on blinddecoding. In Mode 2, Method #5 and Method #6 may be distinguishedthrough L1/L2 or higher layer signaling or may be implicitly checkedaccording to subframe allocation pattern or subframe index.

Index Ordering for Maximizing Backhaul Resources

In the following description, the following assumption is given in orderto use backhaul resources. For description, it is assumed that R-PDCCH(or relay) groups 0, 1 and 2 are present. In this case, since a relayassumes that an R-PDCCH is always present in a first slot of an RB pairin a group (e.g., the group 1) to which the relay belongs, only a secondslot of the RB pair may be used to transmit the R-PDCCH. If the R-PDCCHis transmitted using an RB pair of another group (the group 0 or 2)(that is, if an RA indication is present), it is assumed that not onlythe second slot but also the first slot may be used to transmit theR-PDCCH. This is because the relay interprets an RA indication bit whiledistinguishing between the group to which the relay belongs and thegroup to which the relay does not belong.

FIG. 43 shows an example of placing R-PDCCHs according to group indexorder. In FIG. 43, it is assumed that an RBG is composed of four RBs anda total number of R-PDCCHs is 8.

Referring to FIG. 43, eight R-PDCCHs (RN1 to RN8) may be contiguouslyplaced from an RB index 0 according to group index order (e.g., logicalRB index order). In this case, RN4 belonging to a group 1 may not use afirst slot of an RB pair belonging to a group 0. This is because RBs (RBindexes 0 to 2) before RN4 of the group 1 are filled with R-PDCCHs ofother RNs (RN1 to RN3). In this case, the above-described assumption(that is, the assumption that an R-PDCCH begins to be transmitted fromthe first slot if an RA indication is present in groups other than thegroup 1 to which RN4 belongs) is not suitable. Accordingly, as shown, anew rule is necessary if group index ordering is applied. A group indexordering method should be decided.

As one method, a high index value may be given to an RN to which a BSshould transmit a relatively large amount of data (e.g., a group 2). Incontrast, a relatively low index value may be given to an RN to which aBS should transmit a relatively small amount of data or an RN to whichdata is not transmitted (e.g., a DL grant only case). At this time, inorder to accurately apply the rule, group index ordering may bepreferentially performed according to the amount of data. In suchalignment, the relay may differently interpret RA indication bits whenresources allocated to an RB index lower than that of the relay arepresent and when resources allocated to an RB index higher than that ofthe relay are present, which are shown in FIGS. 44 to 46. FIGS. 44 to 46show different states.

FIG. 44 shows a method of the case in which each RB means a logical RBand index or the case of allocating resources in units of one RB. FIG.45 shows a method suitable for the case of allocating resources in RBGunits. FIG. 45 shows the case in which UL grant is separately packed andis interleaved at a time or in group units having a predetermined size.

FIG. 44 shows the case in which a second slot of an RB pair in which DLgrant of RN2 is present is empty (e.g., a DL grant alone case) and thecase in which empty resources are used for RN6. FIG. 44 shows the casein which data for RN6 is transmitted even in an RB pair which is notused by an RN different from a second slot of an RB pair in which DLgrant of RN6 is present, in addition to the above-described emptyresources. That is, a larger amount of data is transmitted to RN6 ascompared to RN1 or RN2. This is because it is assumed that group indexordering is performed according to the size of data to be transmitted tothe relay. In this case, RA bit interpretation is differently set. Thatis, RA bits for RBs (RBs of the left direction) present before RN6indicates only whether data is present in a second slot. This is becausea first slot is occupied by RNs having low group indexes as in RN2. Whenthe R-PDSCH of RN6 is allocated to RBs (RBs of the right direction)greater than an RB index in which RN6 is present, an RA bit indicateswhether an R-PDCCH is present in both a first slot and a second slot.That is, the relay may perform decoding on the assumption that R-PDCCHsare transmitted at the second slot of the PR pair or all slots inconsideration of a group index. The above assumption may be summarizedas follows:

1. If an RA bit indicates data (e.g., (R-)PDSCH) allocation with respectto RB pair(s) occupied by an R-PDCCH (or an R-PDCCH group) of a relayand previous R-PDCCH(s) (or R-PDCCH group(s) in a search space, therelay assumes that DL grant is transmitted at the first slot of the RBpair and data thereof is transmitted at the second slot. Accordingly,the relay performs (R-)PDSCH decoding on the assumption that data is nottransmitted in the first slot of the RB pair.

2. If an RA bit indicates data (e.g., (R-)PDSCH allocation with respectto RB pair(s) next to the RB pair(s) occupied by the R-PDCCH of therelay in the search space, the relay assumes that data is transmitted inboth the first and second slots of the RB pair. Accordingly, the relayperforms (R-)PDSCH decoding on the assumption that data is transmittedin both the first and second slots of the RB pair.

According to the present proposal, the relay does not need to know howmany RBs are used by the R-PDCCHs in a given subframe or how manyR-PDCCHs are present.

FIG. 45 shows the case of introducing the RBG concept. If resources areallocated in RBG units, only PRBs belonging to the RBG may not be used.As the number of unusable RBs is increased, the above method enablesefficient use of backhaul resources. FIG. 45 shows the case in which 1RB of an RBG to which RN belongs is used for RN2 and R-PDSCHs for RN2are transmitted in an RB pair in which an R-PDCCH of the RN as well asan RBG to which RN2 belongs are not present. In this case, RA bitinterpretation for the RBG index having an index lower than that of anRBG to which RN2 belongs and RA bit interpretation for a PRB having anindex grater than that of the RBG to which RN2 belongs are different.

FIG. 46 shows an example of packing UL grant with lower indexes if ULgrant is less than DL grant. By this configuration, all RBs except forRBs occupied by UL grant may be used for the proposed rule.

The above description focuses upon a relationship between a BS and anRN, but is equally/similarly applied to a relationship between an RN anda UE. For example, in the above description, a BS may be replaced withan RN and an RN may be replaced with a UE.

FIG. 47 shows a BS, an RN and a UE to which the present invention isapplicable.

Referring to FIG. 47, a radio communication system includes a BS 110, anRN 130 and a UE 130. For convenience, although the UE is connected tothe RN, the UE may be connected to the BS.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 is configured to implement theprocedures and/or methods of the present invention. The memory 114 isconnected to the processor 112 so as to store a variety of informationassociated with the operation of the processor 112. The RF unit 116 isconnected to the processor 112 so as to transmit and/or receive an RFsignal. The RN 120 includes a processor 122, a memory 124 and a radiofrequency (RF) unit 126. The processor 122 is configured to implementthe procedures and/or methods of the present invention. The memory 124is connected to the processor 122 so as to store a variety ofinformation associated with the operation of the processor 122. The RFunit 126 is connected to the processor 122 so as to transmit and/orreceive an RF signal. The UE 130 includes a processor 132, a memory 134and a radio frequency (RF) unit 136. The processor 132 is configured toimplement the procedures and/or methods of the present invention. Thememory 134 is connected to the processor 132 so as to store a variety ofinformation associated with the operation of the processor 132. The RFunit 136 is connected to the processor 132 so as to transmit and/orreceive an RF signal. The BS 110, the RN 120 and/or the UE 130 may havea single antenna or multiple antennas.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features.

Also, some structural elements and/or features may be combined with oneanother to constitute the embodiments of the present invention. Theorder of operations described in the embodiments of the presentinvention may be changed. Some structural elements or features of oneembodiment may be included in another embodiment, or may be replacedwith corresponding structural elements or features of anotherembodiment. Moreover, it will be apparent that some claims referring tospecific claims may be combined with other claims referring to the otherclaims other than the specific claims to constitute the embodiment oradd new claims by means of amendment after the application is filed.

The embodiments of the present invention are disclosed on the basis of adata communication relationship among a base station, an RN and a UE.Specific operations to be conducted by the base station in the presentinvention may also be conducted by an upper node of the base station asnecessary. In other words, it will be obvious to those skilled in theart that various operations for enabling the base station to communicatewith the terminal in a network composed of several network nodesincluding the base station will be conducted by the base station orother network nodes other than the base station. The term “Base Station(BS)” may be replaced with a fixed station, Node-B, eNode-B (eNB), or anaccess point as necessary. The term “terminal” may also be replaced witha User Equipment (UE), a Mobile Station (MS) or a Mobile SubscriberStation (MSS) as necessary.

The embodiments of the present invention can be implemented by a varietyof means, for example, hardware, firmware, software, or a combinationthereof. In the case of implementing the present invention by hardware,the present invention can be implemented with application specificintegrated circuits (ASICs), Digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicrocontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention can be implemented in theform of a variety of formats, for example, modules, procedures,functions, etc. Software code may be stored in a memory unit so that itcan be driven by a processor. The memory unit is located inside oroutside of the processor, so that it can communicate with theaforementioned processor via a variety of well-known parts.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

The present invention relates to a radio communication system and isapplicable to a base station, a relay node and a user equipment.

The invention claimed is:
 1. A method for receiving a Relay PhysicalDownlink Control Channel (R-PDCCH) signal at a relay in a wirelesscommunication system, the method comprising: receiving first controlinformation for downlink scheduling in a 1^(st) slot of a set of aresource block (RB) pair, wherein the first control information includesallocation information on one or more resource units; monitoring secondcontrol information for uplink scheduling in a 2^(nd) slot of the set ofthe RB pair; and performing procedures for receiving data correspondingto the first control information, wherein if the allocated one or moreresource units overlap with the RB pair where the first controlinformation is detected, the procedures for receiving data are performedunder an assumption that the data exists on the 2^(nd) slot of the RBpair, when the R-PDCCH is configured to be non-interleaving by highlayer signaling.
 2. The method of claim 1, wherein the allocationinformation on one or more resource units includes a bitmap for resourceallocation, each bit indicating resource allocation of a correspondingRB or a Resource Block Group (RBG).
 3. The method of claim 1, whereinthe monitoring the second control information is performed under anassumption that an aggregation level of the second control informationis less than an aggregation level of the first control information. 4.The method of claim 1, further comprising: receiving information relatedto an arrangement of the second control information on resources of the2^(nd) slot via upper layer signaling.
 5. An apparatus used for awireless communication system, the apparatus comprising: a radiofrequency unit; and a processor configured to: receive first controlinformation for downlink scheduling in a 1^(st) slot of a set of aresource block (RB) pair, wherein the first control information includesallocation information on one or more resource units, monitor secondcontrol information for uplink scheduling in a 2^(nd) slot of the set ofthe RB pair, and perform procedures for receiving data corresponding tothe first control information, wherein if the allocated one or moreresource units overlap with the RB pair where the first controlinformation is detected, the procedures for receiving data are performedunder an assumption that the data exists on the 2^(nd) slot of the RBpair, when the R-PDCCH is configured to be non-interleaving by highlayer signaling.
 6. The apparatus of claim 5, wherein the allocationinformation on one or more resource units includes a bitmap for resourceallocation, each bit indicating resource allocation of a correspondingRB or a Resource Block Group (RBG).
 7. The apparatus of claim 5, whereinthe monitoring the second control information is performed under anassumption that an aggregation level of the second control informationis less than an aggregation level of the first control information. 8.The apparatus of claim 5, wherein the processor is further configured toreceive information related to an arrangement of the second controlinformation on resources of the 2^(nd) slot via upper layer signaling.